As a method for expressing recombinant proteins, a method for mainly using cells such as Escherichia coli and yeast, transforming a recombinant protein expression vector into the cell, and culturing the transformed cells to express proteins has been generally used. The above-described method requires a strain selection process which stably expresses recombinant protein and has a difficulty in expressing protein having toxicity in a cell, such that it takes at least several days to months to obtain one protein.
Recently, a cell-free protein expression method synthesizing protein in a test tube without using cells has received attention, and various products related thereto has been developed. The cell-free protein expression method, which is a system of expressing protein by adding a template DNA capable of expressing protein, for example, an expression vector, a PCR product, a cell lysate, an expression solution, and a diethylpyrocarbonate (DEPC) distilled water into a tube, and performing a reaction at a proper temperature (30 to 40° C.) for a proper time (1 to 3 hours), has an advantage in that proteins having toxicity in a cell are capable of being expressed, and a required time may be remarkably reduced as compared to the above-mentioned method for expressing proteins using cells. Here, in order to express proteins, proper temperature and time are required. The reason is that an activity on an enzyme should be accompanied during all processes including synthesis of RNA from DNA in a tube and synthesis of protein from the RNA, wherein the above-described processes are capable of being performed in the case of maintaining a temperature when activities of a plurality of enzymes are shown, that is, 30 to 40° C.
Since a plurality of proteins are mixed in a sample having expressed recombinant proteins, in order to easily purify the recombinant protein expressed from the sample, the expressed proteins should have an affinity with a specific material. Recently, a method for purification proteins by expressing a coupled state between recombinant protein and histidine and using an affinity of histidine and metal ions (nickel ion, cobalt ion, and the like) has been mainly used, and various products related thereto have been on sale. Among the methods, a method for using magnetic particles has been mainly used, wherein metal ions on a surface of the magnetic particles are coupled with histidine of the target protein, such that the target protein only is capable of being extracted from a plurality of proteins.
However, according to the existing technologies according to the related art, high yield and high-purity purification may not be achieved and it is difficult to control protein complicated expression due to cell culture, which is non-effective, such that a basic issue which is reproducible production on the same proteins still has not been overcome.
Therefore, a method for producing proteins capable of achieving high yield and high-purity purification and having reproducible synthesis efficiency on the same protein is required.